Safety Risk Assessment for Building Excavations Using Monte Carlo Simulation-Based Sensitivity Analysis

Building excavations in urban environments involve significant safety challenges arising from complex geotechnical conditions, adjacent structures, and construction uncertainties. This study proposes an integrated framework for identifying and prioritizing excavation safety risks and for quantitatively assessing their schedule consequences under uncertainty. An initial literature review identified 25 excavation-related safety risks, which were subsequently evaluated using the Fuzzy Delphi Method with input from 25 experts. The evaluated process resulted in the validation of 18 safety risks. The Shannon Entropy method was then employed to determine the relative importance of five project-performance criteria, while the VIKOR method was used to rank the identified risks based on expert assessments from 156 construction professionals. The five highest-ranked risks were transferred to a schedule-focused Monte Carlo Simulation (MCS) of a steel truss-supported excavation project in Karaj, Iran. The Delphi survey screening scores are interpreted as expert-derived plausibility scores and are converted to associated subjective scenario probabilities through proportional possibility-to-probability normalization. The simulation results demonstrated that the inclusion of risk-related uncertainties increased the project duration from 62 days to approximately 132.5 days. A robustness check against equal scenario weights produced only small changes in the representative Phase 1 and Phase 2 expected durations (1.42% and 1.81%, respectively), indicating limited local sensitivity to the selected probability transformation. The principal contribution of the study is the explicit, excavation-specific linkage between expert consensus, multi-criteria risk prioritization, and probabilistic schedule-consequence analysis, and an uncertainty-transformation robustness check.